1. Field of the Invention
The invention relates to an injection nozzle for a mould, for example for synthetic materials, for the production of, for example, hollow objects such as candle glasses and cups. Afterwards the hollow bodies can be blown to form, for example, spheres for lighting bodies.
2. Description of Related Art
Known injection nozzles comprise bodies in several parts with a sprue which accommodates a pin- or slide-type shutoff valve that can be moved back and forth to shut off and leave clear the gate into the mould.
These known nozzles entail certain disadvantages. The presence of moving parts in the sprue and the consequent need to activate them makes it necessary to deflect this sprue at the points where the moving parts act. As a consequence of this the injected fluid strikes said moving parts, downstream of the point of action, from a direction that does not coincide with the axis of the moving parts. This causes variations in speed in the flow of fluid injected into the mould, for which the speed diagram is consequently asymmetric and, in most cases, is not centered upon the axis of the sprue. It also causes an irregular and asymmetric feed of material into the mould and consequent defects in the moulded part, such as nonuniform thickness or temperature, tensions and formation of weld runs between uneven flows of material in the mould cavity. The presence of moving parts in the sprue encourages the stagnation of particles of material inside the sprue. When changing the colour of the material to be injected, residues from the previous job remaining in the sprue are incorporated by the new material with the other colour and create spots and stains of a different colour in the moulded parts. Known nozzles made of several parts are structurally complex and make it difficult to achieve an even temperature along the sprue.